In copending applications of Norman L. Stauffer, Ser. No. 85,821, filed Oct. 17, 1979, now U.S. Pat. No. 4,309,603 and James H. Frazier, Ser. No. 212,930, filed Dec. 4, 1980, and John C. Wittenberger, Ser. No. 212,918, filed Dec. 4, 1980, certain auto focus circuitry is disclosed for use on low cost cameras utilizing very few radiation responsive detectors.
In using a small number of detectors, it becomes extremely important that the outputs of the detectors be closely matched since these systems operate on the principle that as the focus lens moves changing the radiation received by the individual detectors, the proper focus position is reached when the outputs of two detectors are substantially equal. If the detectors are mismatched, the point at which the outputs become equal will not necessarily coincide with the position of best focus for the lens.